1. Field of the Invention
The present invention relates generally to a heat exchanger of the type wherein a plurality of packets of sheet metal are piled up, and more particularly to the heat exchanger of a so-called housing-less type wherein alternate fluid flow paths for fluids are formed in the heat exchanger without using a housing.
2. Description of the Prior Art
In connection with plate type heat exchangers, it has been already proposed that a plurality of packets of sheet metal are piled up and secured to each other to form a so-called housing-less plate type heat exchanger in which a space is formed between the adjacent packets by means of plate type thick distance pieces each of which is interposed between the adjacent packets, thereby forming multiple stages of spaces in which two fluid flow paths for two fluids are formed on alternate stages of spaces. Heat exchanging between the two fluids is accomplished through a packet serving as an interface between the adjacent two fluid paths.
However, drawbacks have been encountered in the thus arranged conventional heat exchanger, in which the above-mentioned plate type thick distance pieces are considerably heavy in weight and therefore contribute to increasing the weight of the heat exchanger, thereby requiring large-sized installation or support means for the heat exchanger. Furthermore, since the distance pieces are usually produced by machining a blank plate material, a higher cost for the production process is required. Moreover, a large amount of heat is required for brazing because the thick distance pieces require a larger amount of brazing metal and are larger in heat capacity, thus increasing the cost for brazing.